Although it has many applications, the present disclosure and the problem addressed thereby is explained in relation to sandwich panels which are designed for cladding passenger cabins of aircraft. In principle, however, the present disclosure can also be used for producing panels for installation in general vehicles, such as road vehicles, railway vehicles and/or watercraft or the like, or in buildings, etc. Panels produced according to the disclosure herein can be used as floor plates, as cladding or cover plates and in the general design of interior spaces.
Because of the good ratio of rigidity or strength to density, sandwich structures or sandwich components, generally referred to in the following as sandwich panels, have a wide range of applications in the field of aircraft construction. Sandwich panels typically consist of a lightweight inner core structure, which is enclosed on either side by a cover layer. By appropriately designing the core structure, both the rigidity of these panels and other properties, such as acoustic or thermal insulation, can be set.
The cover layers are typically made of a fiber composite material, e.g. carbon fiber reinforced plastics material (CFRP). The core structure may for example be honeycomb-like and comprise a plurality of cells having a hexagonal cross section. The cell walls of the honeycomb may be made of a fiber paper impregnated with phenol resin, or of other materials such as cardboard, plastics material, etc. Rigid foam materials are often used as an alternative to a honeycomb construction of this type. These materials have advantages over honeycomb structures, inter alia in the field of thermal and acoustic insulation, and in component production. In order to also ensure sufficient mechanical properties of foam-based core composites in comparison with core composites having a honeycomb-like core structure of a comparable density, techniques are sometimes used in which reinforcing pins, fibers or threads or the like are inserted into rigid foam components. In what is known as the “tied foam core” technique, as described in DE 10 2005 024 408 A1 for example, a foam is penetrated by ‘dry’ fiber bundles by a sewing technique. Following a resin infiltration process and a subsequent curing process, the fiber bundles form rigid pins, which contribute to mechanically reinforcing the foam.
Known methods of this type for reinforcing foam cores are, however, usually only suitable for reinforcing foamed thermosetting polymers. If, however, fibers were accordingly inserted into a thermoplastic foam, it would be difficult in practice to subsequently infiltrate the fibers with a thermoplastic infusion material due to the high viscosity of thermoplastic polymers. However, foams made of thermoplastic polymers can be deformed into practically any shape under the effects of pressure and temperature, and can be joined to thermoplastic face sheets in short cycle times.